This proposal has two main areas of investigation: 1) to examine B cell antigen presentation to T cells, and 2) to characterize antigen processing by macrophages and B cells. Using functional studies, we will examine the ability of B cells to present antigenic determinants, to T cells in a manner similar to macrophages. We will determine if B cell presentation of antigen to T cells is MHC restricted. In addition, we will test the ability of murine lymphoma cells and neonatal B cells to present antigen to T cells. Using functional, biochemical and immunochemical techniques, we will study the physical and immunological characteristics of macrophage and B cell antigen processing. Characterization will include studies of antigen degradation and the involvement of lysosomes in antigen processing. Using both intact macrophages and B cells and subcellular fractions of these cells, we will study the characteristics of immunologically active processed antigen and its possible association with MHC gene products.